B1h Flashcards
What are environmental and inherited characteristics arguments?
Intelligence - one theory is that although your maximum possible IQ might be determined by your genes, whether you get to it depends on your environment, e.g. your upbringing and school life.
Body mass/ height - both environmental and inherited
Health - some people are more likely to get certain diseases like cancer and heart disease because of their genes. But lifestyle also affects the risk, if you smoke or only eat junk food.
Sporting ability - genes determine your potential, but training is important too.
Where are chromosomes held and what do they do?
Chromosomes are held in the nucleus and they carry information in the form of genes, which control inherited characteristics.
What do most body cells contain chromosomes in?
Matched pairs.
What do gametes have?
Half the number of chromosomes of body cells.
What are the causes of genetic variation?
Mutations - occasionally a gene may mutate creating new characteristics, increasing variation.
Gamete formation - sperm or egg cells formed in the testes or ovaries. The body cells they’re made from have 23 pairs of chromosomes. In each pair there’s a chromosome that was originally inherited from mum, and one from dad. When these body cells split to form gametes the chromosomes are also split up. This means that gametes end up with half the number of chromosomes of a normal body cells - 23. In each gamete some of dads are grouped with some of mums. This shuffling up of chromosomes leads to variation in the new generation.
Fertilisation - when the sperm and the egg, with 23 chromosomes each, join to form a new cell with the full 46 chromosomes. Fertilisation is random so you don’t know which two gametes are going to join together.
What are alleles?
Different versions of the same gene.
How is sex in mammals determined by sex chromosomes?
XX female
XY male
How do dominant and recessive characteristics depend on dominant and recessive alleles?
Most of the time you have two of each gene (two allele) - one from each parent.
If the alleles are different you have instructions for two different versions of a characteristic, e.g. blue eyes or brown eyes, but you only show one version of the two, e.g. brown eyes. The version of the characteristic that appears is caused by the dominant allele. The other allele is recessive. The recessive allele is only expressed if there is no dominant allele present.
What is homozygous?
if you’re homozygous for a trait you have two alleles the same for that particular gene e.g. CC OR cc.
What is heterozygous?
If you’re heterozygous for a trait you have two different alleles for that particular gene, e.g. Cc
What is genotype?
Your genetic makeup, the alleles you have for a particular gene, is known as your genotype.
What is phenotype?
The characteristics alleles produce (e.g. brown eyes) is known as your phenotype.
What is a monohybrid cross?
When you breed two organisms together to loom at a characteristic that’s controlled by one gene.
What is sex inheritance, using genetic diagrams?
There’s an equal chance of having a boy or a girl. When you put all the letters in the diagram, it shows that there are two XX results and two XY results, so there’s the same probability of getting a boy or a girl. This 50:50 ratio is only a probability.
What disorders are inherited?
Red-green colour blindness.
Sickle cell anaemia.
Cystic fibrosis - causes the body to produce a lot of thick, sticky mucus the air passages and in the pancreas.
What are inherited disorders caused by?
Faulty genes. The allele which causes it is a recessive cell carried by about 1 person in 25. Because its recessive, people with only one copy of the allele won’t have the disorder - they’re known as carriers. for a child to have a chance of inheriting the disorder, both parents must either be carriers or sufferers. There’s a one in four chance of a child having the disorder if both parents are carriers.
What are the issues raised by knowledge of inherited disorders in a family?
Should all family members be tested to see if they’re carriers? Some people might prefer not to know, but is this fair on any partners or future children they might have?
Is it right for someone who’s at risk of passing on a genetic condition to have children? Is it fair to put them under pressure not to, if they decide they want children?
If the test is positive, is it right to terminate the pregnancy? The family might not be able to cope with a sick or disabled child, but why should they have a lesser right to live than a healthy child?
